Because of the particular location where they are used, which is mostly arranged within the machine housing (also referred to as the nacelle) of the wind turbine, electrical and/or electronic subassemblies in wind turbines, for example converters (also called inverters), are exposed to exceptionally harsh environmental conditions. In particular, they are subject to severe vibrations from the wind and the operation of the rotors, together with high temperature fluctuations due to irregular operating cycles and because of the rapidly changing external temperatures, where these changes have in addition large amplitudes. This applies for both their operation in offshore wind turbines and also in onshore wind turbines, while in the case of offshore operations there are additional factors which have an influence, such as the more frequent occurrence of storms and the associated (salt-containing) spray, which further aggravate the environmental conditions. In sum, this means that electrical and/or electronic subassemblies of this type are subject to severe wear and tear, even though they are mostly arranged in the shrouding of the machine housing.
At the same time, an unexpected failure of a single such electric and/or electronic subassembly in a wind turbine implies very high outlay on additional maintenance deployments and costs. For this reason, the objective is generally to maintain such subassemblies, for example as part of regular maintenance work, by a regular program of replacements, so that a failure does not occur suddenly and unexpectedly, by which means additional downtimes can be avoided.
It is correspondingly important to provide highly-reliable options for correctly estimating a time point for maintenance, in order to be able to react early enough, that is before the electrical and/or electronic subassembly fails. Presently, the monitoring of subassemblies consists mainly of pure fault monitoring, i.e. an indication is given when a subassembly has already failed. In order to deal with such outages, the maintenance intervals are in addition deliberately kept very short, and to be safe it is preferred that a subassembly is replaced prematurely. This in turn brings the consequence that the material and labor usage in relation to these electrical and/or electronic subassemblies is generally higher than would actually be technically necessary.
Even if such a maintenance time point is accurately determined, the problem still remains that this maintenance time point can be even before a time point for maintenance at a planned maintenance interval, i.e. that the subassembly is expected to fail even before maintenance staff next arrive at the wind turbine. This means that staff must be sent out to the wind turbine prematurely, i.e. outside the maintenance cycle, in order to undertake unplanned maintenance, which is associated with corresponding additional cost.